Communication devices used in a high frequency band such as BS/CS broadcasting devices, microwave communication devices, and radar devices are increasingly used in recent years. In general, with a higher frequency, energy attenuation of electromagnetic wave becomes greater when propagating through a substance having a high relative permittivity. As a result, there is a problem of deteriorated communication performance. For this reason, in an electronic component of a communication device, there has been employed an airtight sealing structure in which an air layer, which has a low relative permittivity, is formed around an element part of an electronic component to thereby seal it in a hollow space, in order to sufficiently bring out its high frequency characteristic.
In electronic components, there are required various types of characteristics including high performance, superior reliability, miniaturization, and cost reduction. In addition to improvements to the element part itself, there is a need for improving the package that seals an element in a hollow space (hollow sealing structure). Examples of requirements for a hollow sealing structure include superior air tightness, cost reduction, and ensuring sufficient mounting area.
As a hollow sealing structure that seals an element part in a hollow space, for example, a hollow sealing structure proposed in Patent Document 1 includes a substrate, an element part provided on the substrate, a resin cap that covers and hollow-seals the element part, and an adhesion part that adheres the resin cap onto the substrate. The resin cap has a fixation film.
A configuration proposed in Patent Document 2 includes a substrate, an element part provided on the substrate, and a cap that covers and hollow-seals the element part. On the substrate, there is provided a step for positioning the cap.
Moreover, a configuration proposed in Patent Document 3 includes a substrate with a hole formed therein, an element part provided on the substrate, and a cap that hollow-seals the element part and that has a projection part provided thereon. The projection part of the cap is arranged in the hole of the substrate and fixes the cap.